Determination of Bromine and Iodine in Rock, Soil, and Sediments by Inductively Coupled Plasma-Mass Spectrometry Using Pyrohydrolysis with Liquid Nitrogen Trap

The available extraction methods for the determination of Br and I in geological samples, include semifusion, aqua ammoniae closed digestion and pyrohydrolysis. The sample digestion and extraction of Br and I are the major error sources, due to the low content and volatization of Br and I. A pyrohydrolysis method with liquid nitrogen trap has been developed and used to extract Br and I in geological samples using liquid nitrogen condensation absorption replacing alkaline solution absorption. Br and I are measured by Inductively Coupled Plasma-Mass Spectrometry. The detection limits of Br and I are 0.06 μg/g and 0.01 μg/g, respectively, calculated as 10 times standard deviation using dilution times of 50. These detection limits are lower than those of traditional pyrohydrolysis and semifusion methods and slightly higher than those of aqua ammoniae closed digestion method. The precision is 6.4%-21.0% RSD. The proposed method reduces the use of alkaline solution, lowers the blank and dilution times, and improves the precision. This method is much simpler than the semifusion method and can serve as a complementary method for aqua ammoniae closed digestion method. For soils and stream sediments, aqua ammoniae closed digestion method is preferred. For rocks and samples that cannot be completely digested by aqua ammoniae closed digestion method, the proposed method may be more suitable.